Impacts of Climate Change on Microbial Activity in Agricultural …
101
Table 2 Some substantial soil enzymes and their functions
Enzyme
Function
Reaction
Microbial activity
indicator
Amidase
Hydrolysis of C–N
bonds other than
peptide bonds in
linear amides
R-CONH 2 + H 2 O
→ NH 3 + R-COOH
N-cycling
Urease
Hydrolysis of urea
into ammonium and
carbon oxide
Urea + H 2 O → CO 2
+ 2NH 3
N-cycling
Phosphatase
Hydrolysis of
ester-phosphate bond
and release of
phosphate
RNa 2 PO 4 + H 2 O →
R-OH + Na 2 HPO 4
P-cycling
Sulfatase
(arylsulfatase)
Hydrolysis of
organic-sulfate ester
releasing inorganic
sulfate
R-O-SO
−
3 + H 2 O →
R-OH + H + + SO
2−
4
S-cycling
β-glucosidase
Hydrolysis of
cellulose
Glucoside-R + H 2 O
→ glucose + R-OH
C-cycling
Dehydrogenase
Electron transport
system
XH 2 + A → X +
AH 2
Endoenzyme
Source Acosta-Martinez and Tabatabai [25], Gianfreda and Ruggiero [26], Skujins [27]
significantly correlated with some soil microbial parameter like microbial biomass
and respiration [22]. Dehydrogenase is an endoenzyme and used as bioindicators
and relating to soil fertility. The dominant soil enzymes that play a vital role in the
decomposition of organic compounds and nutrient cycling in the soil are summarized
in Table 2.
Soil microorganisms such as bacteria, fungi, actinobacteria, mycorrhizae and
cyanobacteria have the enzyme of urease. This enzyme plays an essential role for
degradation or hydrolysis of organic matter in agricultural soils. For example, ElShinnawi [28] studied the activity of urease in different Egyptian soils treated with
0 and 5% farmyard manure and adjusted moisture at 50, 65 and 80% of the water
holding capacity (WHC). He found that the activity of urease is very varied based
on the soil type and the order of activity was the following: fertile, saline, alkali,
calcareous, and sandy soil. Application of farmyard manure led to slightly increased
the urease activity, and the optimum of moisture is 50% of WHC for the tested
soils. These findings are in agreement with a study of Elsoury et al. [29], showing
the addition of compost or farmyard manure significantly increased soil microbial
biomass when compared to mineral fertilizers. The activity of urease, phosphatase
and dehydrogenase significantly increased in wheat rhizospheric soil treated with
organic amendments when compared to mineral fertilizer under field experiment in
Burg El-Arab region, Egypt. The degradation of plant and animal organic nitrogen
wastes in soils using urease-producing microorganisms leads to eliminate the vast
101
Table 2 Some substantial soil enzymes and their functions
Enzyme
Function
Reaction
Microbial activity
indicator
Amidase
Hydrolysis of C–N
bonds other than
peptide bonds in
linear amides
R-CONH 2 + H 2 O
→ NH 3 + R-COOH
N-cycling
Urease
Hydrolysis of urea
into ammonium and
carbon oxide
Urea + H 2 O → CO 2
+ 2NH 3
N-cycling
Phosphatase
Hydrolysis of
ester-phosphate bond
and release of
phosphate
RNa 2 PO 4 + H 2 O →
R-OH + Na 2 HPO 4
P-cycling
Sulfatase
(arylsulfatase)
Hydrolysis of
organic-sulfate ester
releasing inorganic
sulfate
R-O-SO
−
3 + H 2 O →
R-OH + H + + SO
2−
4
S-cycling
β-glucosidase
Hydrolysis of
cellulose
Glucoside-R + H 2 O
→ glucose + R-OH
C-cycling
Dehydrogenase
Electron transport
system
XH 2 + A → X +
AH 2
Endoenzyme
Source Acosta-Martinez and Tabatabai [25], Gianfreda and Ruggiero [26], Skujins [27]
significantly correlated with some soil microbial parameter like microbial biomass
and respiration [22]. Dehydrogenase is an endoenzyme and used as bioindicators
and relating to soil fertility. The dominant soil enzymes that play a vital role in the
decomposition of organic compounds and nutrient cycling in the soil are summarized
in Table 2.
Soil microorganisms such as bacteria, fungi, actinobacteria, mycorrhizae and
cyanobacteria have the enzyme of urease. This enzyme plays an essential role for
degradation or hydrolysis of organic matter in agricultural soils. For example, ElShinnawi [28] studied the activity of urease in different Egyptian soils treated with
0 and 5% farmyard manure and adjusted moisture at 50, 65 and 80% of the water
holding capacity (WHC). He found that the activity of urease is very varied based
on the soil type and the order of activity was the following: fertile, saline, alkali,
calcareous, and sandy soil. Application of farmyard manure led to slightly increased
the urease activity, and the optimum of moisture is 50% of WHC for the tested
soils. These findings are in agreement with a study of Elsoury et al. [29], showing
the addition of compost or farmyard manure significantly increased soil microbial
biomass when compared to mineral fertilizers. The activity of urease, phosphatase
and dehydrogenase significantly increased in wheat rhizospheric soil treated with
organic amendments when compared to mineral fertilizer under field experiment in
Burg El-Arab region, Egypt. The degradation of plant and animal organic nitrogen
wastes in soils using urease-producing microorganisms leads to eliminate the vast